The Use of Multisource Optical Sensors to Study Phytoplankton Spatio-Temporal Variation in a Shallow Turbid Lake

Lake water quality monitoring has the potential to be improved through integratingdetailed spatial information from new generation remote sensing satellites with high frequencyobservations from in situ optical sensors (WISPstation). We applied this approach for Lake Trasimenowith the aim of increasing knowledge of phytoplankton dynamics at dierent temporal and spatialscales. High frequency chlorophyll-a data from the WISPstation was modeled using non-parametricmultiplicative regression. The 'day of year' was the most important factor, reflecting the seasonalprogression of a phytoplankton bloom from July to September. In addition, weather factors such asthe east-west wind component were also significant in predicting phytoplankton seasonal and diurnalpatterns. Sentinel 3-OLCI and Sentinel 2-MSI satellites delivered 42 images in 2018 that successfullymapped the spatial and seasonal change in chlorophyll-a. The potential influence of localized inflowsin contributing to increased chlorophyll-a in mid-summer was visualized. The satellite data alsoallowed an estimation of quality status at a much finer scale than traditional manual methods. Goodcorrespondence was found with manually collected field data but more significantly, the greatlyincreased spatial and temporal resolution provided by satellite and WISPstation sensors clearly oersan unprecedented resource in the research and management of aquatic resources.